A contemporary hard disk drive includes at least one disk and accesses at least one of its two disk surfaces as the disk rotates at several thousand revolutions per minute. Typically, the data stored on the disk is organized in tracks, often arranged as concentric circles about the center of the disk.
Data access is usually performed through track read and track write operations. To perform either of these operations, a read-write head embedded flies in a slider a short distance off of the rotating disk surface, known as the flying height. The track pitch, or distance from the center of one data track to a neighboring track and the flying height may be less than ten nanometers. Positioning the read-write head to write a track is a significant technical challenge and has significant consequences on the overall quality and performance of the hard disk drive. Should the head be improperly positioned, it can damage the contents of a neighboring data track.
What is needed are ways to improve the reliability of writing data tracks by minimizing effects on neighboring data tracks.
Contemporary practice for writing a data track uses a position error signal based upon two of the four servo offset burst patterns, known as A burst, B burst, C burst, and D burst. Usually, the position error signal is generated from the A burst and B burst to control the positioning of the write head during writing operations. Typically the write head and the read head are not positioned over the same track, but are offset by several data tracks.